Size-controlled synthesis of anatase TiO2 nanoparticles was carried out by using metatitanic acid as a starting material and in the presence of carboxylic acid group-containing organics as modifiers. The average particle sizes and particle size distributions of the resulting anatase TiO2 nanoparticles were significantly affected by the chemical structures of the organic modifiers. The presence of nonpolar group-containing carboxylic acids was beneficial to formation of small-sized and narrow size-distributed anatase TiO2 nanoparticles. © 2005 Elsevier B.V. All rights reserved.